1. Field of the Invention
The present invention relates to a magnetic disk drive for reading information stored in a recording disk and/or writing information to the recording disk, and in particular to a magnetic disk drive suitable for high density recording.
2. Description of Background Art
Recently, the use of small-sized portable Winchester magnetic disk drives has been rapidly developing.
Therefore, as a result of these recent developments, the track density of the magnetic disk has been improved. Also, the use of small-sized portable actuators has been rapidly developing. The actuator is capable of high speed access.
The above magnetic disk drive is explained with reference to FIG. 1 and FIG. 2.
As shown in FIG. 1, in the technology disclosed in Japanese Patent Publication No. 1-294278, a magnetic disk drive 1 comprises a head slider 2 to which a transducer of a magnetic head is attached, an arm assembly 3 for moving the head slider 2 rotatably, a pivot 4 which is positioned at the rotation center of the arm assembly 3, a suspension 5 which carries the magnetic head and connects the head slider 2 to the arm assembly 3, and a drive motor 6 for driving the arm assembly 3. Also, the pivot 4 comprises a pair of miniature ball bearings, and a shaft which is supported in a freely rotatable manner by the miniature ball bearings.
The head slider 2 is attached to the transducer for reading or writing information stored in a recording disk 7.
In the above structure, position information stored in the recording disk 7 is read by the transducer and fed back to the drive motor 6. In this operation, a positioning servo system is formed in the magnetic disk drive for positioning the actuator. Therefore, the information can be stored in the recording disk at high density and accessed by the head slider 2 at high speed.
However, in the above structure, the pivot 4 is included in the servo system so that the servo system is inclined to be unstable as the rigidity of the pivot 4 is reduced. Therefore, ball bearings having a superior rigidity are utilized in the pivot 4 and the bearings must be made with high accuracy. As a result, a large number of parts is required in the actuator even if the magnetic disk drive becomes small. Also, many processes are required for making the actuator so that the assembly accuracy of the actuator tends to be lowered.
Also, the actuator must be made of aluminum alloys or magnesium alloys. Therefore, the actuator is heavy so that the drive current for driving the actuator becomes large and a servo band tends to be narrowed. Also, the head slider 4 is easily caused to deviate by external shock. Moreover, two pairs of ball bearings are needed to drive the pivot 4 so that the production of the thin magnetic disk drive is difficult.
To solve the above drawbacks, a small-sized magnetic disk drive is proposed in U.S. Pat. No. 4,300,176. Also, the U.S. Pat. No. 4,751,597 is proposed as shown in FIG. 2. In the proposed magnetic disk drive shown in FIG. 2, a pivot 11 is arranged at one end of an arm assembly 12 and a drive motor 13 is arranged at another end of the arm assembly 12, that is near to a head slider 14. As compared with the magnetic head shown in FIG. 1, the arm assembly 12 is curved by 90 degrees. Therefore, the arm assembly 12 is elongated and weighted so that the magnetic head shown in FIG. 2 requires the use of relatively large bearings 15 in the pivot 11. In other words, the pivot 13 is as large as the pivot 5. This means that the magnetic head shown in FIG. 2 still has many parts and the assembly accuracy of the actuator still tends to be lowered.
Also, coils in the drive motor 13 for driving the head slider 14 are positioned near to the head slider 14, and the magnetic flux generated by the coils is directed to the head slider 14. Therefore, noises caused by the magnetic flux is apt to occur. This means that the magnetic disk drive shown in FIG. 2 is not suitable for high density recording.
Moreover, two pairs of ball bearings are required for operating the magnetic disk drive so that the production of a thin and small magnetic disk drive is difficult.